The present invention relates to a wrapping method for rigid cigarette packets.
The invention finds application to advantage in wrapping machines as used to manufacture cigarette packets of the type comprising a cupped body and a lid disposed coaxially in relation to the body, of which the two smaller side or flank faces are incorporated as pairs of longitudinal flaps joined in overlapping contact and glued together.
In conventional machines of the type in question, each successive packet is fashioned typically by advancing a die-cut blank of wrapping material together with a respective group of cigarettes enveloped in a sheet of foil paper along a predetermined first direction, following a first feed path, and folding the blank gradually about the group of cigarettes to the point of producing a partly formed packet, that is to say a packet in which one longitudinal flap of each pair projects laterally from a front face of the body and lid, as yet uncompleted, and the remaining flap of the pair is bent to a right angle. The partly formed packets advance along the first path in this configuration, with the respective longitudinal flaps transversely disposed, toward a transfer station where each packet in turn is engaged axially by its end faces through the agency of a transfer device invested with alternating movement across the first feed path and in a second direction transverse to the first direction.
Thereafter, each of the partly formed packets is repositioned with the respective longitudinal flaps parallel to the second direction and directed thus along a second path that extends through a gumming station, where glue is applied to selected portions of the flaps, and through a folding station where the projecting flaps are bent inwards to a right angle and stuck to the flaps folded previously, thereby completing the packet.
Conventionally, the transfer of each packet from the first path to the second path is effected by engaging the end faces of the cupped body and the lid at one and the same time and thus applying a rigid restraint to the partly formed packet, given firstly that the blank tends naturally to spring back toward its initial flat configuration notwithstanding that dabs of glue will already have been applied to certain points on the inside of the body, and secondly that the lid is completely free to unfold having received no glue on any part as yet.
The method briefly outlined above has certain drawbacks which derive chiefly from the transfer of the packets between the first and the second path, inasmuch as the transfer device is relatively slow in comparison to the conveying devices with which it is associated, and tends also to engage each single packet in a decidedly abrupt manner, not least in order that the transfer operation will be brought about more speedily. Being intermittent in operation, moreover, transfer devices of the type in question are not able to exceed a given maximum output speed, since at speeds higher than the intended maximum the resulting vibrations will be such as to jeopardize the structure and reliability of the machine as a whole.